In a known way, exterior trims fitted to sealing profile strips of the run channel or window sealing strip type for the mobile glazing of a motor vehicle perform a function of decorating or improving the appearance of the sealing profile strips that they cover and these trims, like the sealing profile strips that accept them, are generally made of rigid profile strips (typically made of metal or, by way of alternative, of a rigid or semi-rigid thermoplastic material, the latter then including a reinforcing structure) which are assembled onto the corresponding profile strips. These exterior trims can be attached to the bodyshell of the vehicle, in which case they are called “gutters” or double lip seal against bodyshell, or alternatively to a door of the vehicle, they in this case being exterior door frame trims, whether these be vertical or horizontal. Among such glass run channel exterior trims for hidden frame doors a distinction is usually made, in the case of the extruded profile strips, between:                a first family which includes trims which are attached directly to the rebate of the door frame and to which the glass run channel and the double lip seal portion are added,        a second family which includes trims which are attached to the door frame and which also pass through the sealing profile strip which acts as a double lip seal and a glass run channel, and        a third family which includes trims which are attached to the profile strip that forms the glass run channel, but without making direct contact with the door frame.        
Exterior trims in this first family are usually extruded metal held on the rebate of the door frame by added metal clamps, screws or pop rivets. A major disadvantage with these trims is that they often require re-machining or rework operations (bending to shape the ends, curving to follow the curvature of the frame, molding to sort out the ends if these ends are not bendable in the case of steel), the addition of end fittings and finally machining to prepare regions at which these clips can be fitted.
Other disadvantages with known trims from this first family lie in the surface treatment and/or painting operation (for the “full gloss” black appearance), depending on the appearance desired: chrome, full gloss black, matt, gun metal, etc., in their high cost of manufacture, in the use of aluminum or stainless steel to avoid corrosion (the latter material in fact being very difficult to bend at the ends), in their relatively high weight, and even in the need to bond the trim if its shape evolves over its length.
Document EP-B1-1 232 887 discloses an exterior trim for a door with hidden frame which is injection molded from a thermoplastic material and has a cross section substantially in the shape of a T and is for example force-fitted via a U-shaped clamping portion that it includes onto a flat door frame rebate. This rebate may terminate in an arrowhead-shaped axially external end.
The trim described in that document has the notable disadvantage of being difficult to mold because of the small dimensions and continuity of its U-shaped clamping portion. Another disadvantage with this trim is that it is unable by itself to support the double lip seal profile strip for sealing against the bodyshell with which strip it is simply in contact.